The present invention pertains to collapsible umbrellas for personal use as are typically used for protection from the sun. In particular, the present invention is an umbrella including an improved hub design providing easy and durable operation for umbrellas of the larger sizes and weights.
Such umbrellas are generally known in the prior art. U.S. Pat. No. 5,193,566 to Chen; U.S. Pat. No. 5,247,956 to Vincent; U.S. Pat. No. 6,076,540 to You; U.S. Pat. No. 6,314,976 to Clarke; and U.S. Pat. No. 6,298,867 to Chang disclose various designs which attempt to resolve some of the weaknesses of the collapsible umbrella concept. Particularly, many umbrellas suffer from high weight which makes their manual operation difficult by the user. High weight is a problem directly, and indirectly as producing friction between the relatively moving parts during erection of the umbrella canopy. In addition, as devices often used outdoors in conditions introducing grit and moisture to the umbrella parts, umbrellas are susceptible to corrosion and wear which further hamper operation by users and produce a need for repair. Prior art umbrellas do not provide sufficiently smooth operation for manual operation by single person users, particularly in larger umbrellas. The Vincent patent illustrates one typical design where umbrella ribs and spreaders are pivotably attached at the upright pole by means of wires passing through holes in rib and spreader proximal ends, respectively. While the wires provide an axis of rotation for the moving ribs and spreaders, the rotational friction is inherently high in such a design. In addition, due to the small bearing area between the wire and the rib or spreader hole, high bearing forces produce a high level of wear and deterioration of the parts, increasing the problem. These events are accelerated by environment moisture and grit. In any umbrella design where the bearing area is small at the point of rotation of the ribs and spreaders, bearing and friction forces will likely be a source of problems for the user.
In addition, the design of prior art umbrellas do not provide for easy disassembly for maintenance or replacement of parts. What is needed is an improved umbrella hub design that provides for durable and low friction movement of the umbrella elements during opening and closing operations of the umbrella and provides for easy maintenance and repair.